Percent of Change Task Cards TASK CARD 01
Price Jump
A pair of designer shoes increased in price from $120 to $150.
Retail Scenario
TASK CARD 02
Waste Cut
A factory reduced its monthly chemical waste from 800 gallons to 600 gallons.
Environment
TASK CARD 03
Crowd Growth
The number of students in the Chess Club grew from 20 members to 28 members.
Social Statistics
TASK CARD 04
Battery Life
After a software update, a phone's battery life dropped from 10 hours to 8.5 hours.
Technology
TASK CARD 05
Plant Height
A sunflower was 40 cm tall on Monday and 52 cm tall by Friday.
Biology
TASK CARD 06
Season Sale
A winter coat originally priced at $200 is now marked down to $130.
Retail
TASK CARD 07
Speed Up
An athlete improved their 100m sprint time from 12.5 seconds to 11 seconds.
Athletics
TASK CARD 08
Stock Error
An inventory check showed 500 units in stock, but 50 units were damaged and removed.
Logistics
TASK CARD 09
Social Reach
An influencer's following grew from 2,500 to 4,000 in one month.
Media
TASK CARD 10
Cool Down
The temperature in a server room dropped from 80°F to 68°F after repairs.
Facilities
TASK CARD 11
App Usage
Daily active users for a new app rose from 150 to 225.
Software
TASK CARD 12
Gas Prices
The price of gas went from $3.20 to $3.60 per gallon.
Cost of Living
Change Dynamics Lesson Plan Lesson Plan
Growing and Shrinking
Topic: Calculating Percent of Change
Grade Level
9th Grade / Algebra 1
Duration
65 Minutes
Materials
Slides, Task Cards, Worksheet, Exit Ticket
Learning Objective
Students will be able to calculate the percent of change (increase or decrease) between two given values and apply the formula to real-world problem-solving scenarios.
Key Concepts
Percent of Change: The ratio of the amount of change to the original amount.
Percent Increase: When the new value is greater than the original value.
Percent Decrease: When the new value is less than the original value.
Original Value: The starting amount (always the denominator).
Instructional Arc
10 mins
Introduction & Hook
"The Sneaker Stock Market"
Display sneaker resale prices. Ask: "Which pair gained the most value?" Compare raw dollar growth vs. percentage growth to demonstrate why percentages are useful for relative comparison.
15 mins
Direct Instruction
Introduce the formula clearly. Focus on the absolute value for change and the importance of the original value.
\[ \text{Change \%} = \frac{|\text{New} - \text{Original}|}{\text{Original}} \times 100 \]
15 mins
Guided Practice
Work through "Before and After" problems 1 & 2. Use a "Show Me" whiteboard check or hand signals to identify Increase vs. Decrease before students start calculating.
15 mins
Task Card Sprint
Students cycle through 12 Task Cards placed around the room. Encourage them to verify their partner's "Original Value" identification before moving on to the calculation.
10 mins
Assessment
Collect the Exit Ticket. Review one tricky card (e.g., population growth vs. time decrease) as a final class discussion point.
Differentiation
Support
Provide color-coded formula cards (Original = Red, New = Blue).
Scaffolded worksheet with subtraction steps pre-written for Card 1.
Strategic pairing for the Sprint activity.
Challenge
Find the *new value* given original and percent.
Compare consecutive changes (e.g., two 10% increases vs. one 20% increase).
Apply to stock market data with commission fees.
Checking Out Exit Ticket Exit Ticket
Checking Out
Percent of Change Assessment
Student Name
1. A vintage vinyl record was worth $40 in 2020. Today, its market value is $58 . Calculate the percent of change and circle the direction.
Answer: _____________%
INC DEC
2. A smartphone battery lasted 16 hours when new. After 2 years, it lasts 10 hours . Calculate the percent of change.
Answer: _____________%
INC DEC
Exit Ticket
Checking Out
Percent of Change Assessment
Student Name
1. A vintage vinyl record was worth $40 in 2020. Today, its market value is $58 . Calculate the percent of change and circle the direction.
Answer: _____________%
INC DEC
2. A smartphone battery lasted 16 hours when new. After 2 years, it lasts 10 hours . Calculate the percent of change.
Answer: _____________%
INC DEC
Before and After Worksheet Before & After
Percent of Change Practice
Name
Date
The Master Formula
\[ \text{Change \%} = \frac{\text{Amount of Change}}{\text{Original Amount}} \times 100 \]
Pro Tip
The ORIGINAL value is always your denominator!
A Guided Practice
1. Last year, the average temperature in May was 68°F . This year, it was 74.8°F . Find the percent of change.
Change Amount
Original Amount
Final % Change
Direction:
Increase
Decrease
2. A high-end camera was originally priced at $2,400 . It is now on sale for $1,800 . Find the percent of change.
Change Amount
Original Amount
Final % Change
Direction:
Increase
Decrease
3. A streaming service subscription increased from $12.99 to $15.99 per month. Find the percent of change (round to nearest tenth).
Change Amount
Original Amount
Final % Change
Direction:
Increase
Decrease
4. A local park's pond had 150 ducks last summer. This summer, researchers only counted 114 ducks . Find the percent of change.
Change Amount
Original Amount
Final % Change
Direction:
Increase
Decrease
B Sprint Recording Sheet
12 Real-World Scenarios
Card 01
INC DEC
______%
Card 02
INC DEC
______%
Card 03
INC DEC
______%
Card 04
INC DEC
______%
Card 05
INC DEC
______%
Card 06
INC DEC
______%
Card 07
INC DEC
______%
Card 08
INC DEC
______%
Card 09
INC DEC
______%
Card 10
Change Dynamics Slides Growing and Shrinking
Calculating Percent of Change
Today's Mission
You will be able to calculate the percent of change (increase or decrease) between two given values and apply it to real-world problems.
The Sneaker Game
JANUARY
Retro High OG
$180
JUNE
Retro High OG
$245
"How much did the value grow as a percentage of the original price?"
Key Vocabulary
Percent Increase
When the new amount is greater than the original amount.
Percent Decrease
When the new amount is less than the original amount.
The Master Formula
\[ \text{Percent Change} = \frac{\text{Amount of Change}}{\text{Original Amount}} \times 100 \]
Amount of Change = | New Value - Original Value |
Always use the STARTING value as the denominator!
Steps to Success
01
Subtract the values to find the amount of change .
02
Identify the original (starting) amount.
03
Divide the change by the original amount.
04
Multiply by 100 to convert to a percentage.
Example 1: Growth
A company's stock price was $40 in May and rose to $55 in June. What is the percent increase?
Change: 55 - 40 = 15
Original: 40
Solution: 37.5%
Example 2: Decay
A new laptop costs $1,200. One year later, its resale value is $840. What is the percent decrease?
Change: 1200 - 840 = 360
Original: 1200
Solution: 30%
Danger Zone!
Students often use the Larger Number as the denominator.
Always ask: "Where did we START?"
Task Card Sprint
Ready, Set, Calculate!
Move around the room to find the 12 task cards.
Record your work on the worksheet provided.
Circle whether each card is an Increase or Decrease.
Percent of Change Task Cards Presentation TASK CARD
SPRINT
12 Real-World Scenarios
CARD 01
Retail Scenario
Price Jump
A pair of designer shoes increased in price from $120 to $150.
Calculate the Percent of Change
CARD 02
Environment
Waste Cut
A factory reduced its monthly chemical waste from 800 gallons to 600 gallons.
Calculate the Percent of Change
CARD 03
Social Statistics
Crowd Growth
The number of students in the Chess Club grew from 20 members to 28 members.
Calculate the Percent of Change
CARD 04
Technology
Battery Life
After a software update, a phone's battery life dropped from 10 hours to 8.5 hours.
Calculate the Percent of Change
CARD 05
Biology
Plant Height
A sunflower was 40 cm tall on Monday and grew to 52 cm by Friday.
Calculate the Percent of Change
CARD 06
Retail
Season Sale
A winter coat originally priced at $200 is now marked down to $130.
Calculate the Percent of Change
CARD 07
Athletics
Speed Up
An athlete improved their 100m sprint time from 12.5 seconds to 11 seconds.
Calculate the Percent of Change
CARD 08
Logistics
Stock Error
An inventory check showed 500 units in stock, but 50 units were damaged and removed.
Calculate the Percent of Change
CARD 09
Media
Social Reach
An influencer's following grew from 2,500 to 4,000 in one month.
Calculate the Percent of Change
CARD 10
Facilities
Cool Down
The temperature in a server room dropped from 80°F to 68°F after repairs.
Calculate the Percent of Change
CARD 11
Software
App Usage
Daily active users for a new app rose from 150 to 225.
Calculate the Percent of Change
CARD 12
Cost of Living
Gas Prices
